In processing petroleum oil it is almost invariably necessary to heat the oil to an elevated temperature by contacting it with a heated metal surface, e.g., by flowing it through a heating device such as a tube-and-shell heat exchanger or through the tubes of a direct-fired heater. Many petroleum oils, however, tend to foul metal surfaces with which they come in contact at elevated temperatures by depositing thereon solid or semi-solid materials such as inorganic salts, coke, tars, polymers and other carbonaceous matter. Such fouling materially reduces the efficiency of heat transfer from the metal surface to the oil, thereby increasing the amount of fuel required to heat the oil to the desired temperature. It also reduces the hydraulic capacity of the heat exchange equipment (thereby increasing the amount of energy required to pass the oil through the equipment) and in aggravated cases may render it impossible to maintain the desired flow rate.
The object of the present invention is to provide a means for reducing the fouling of metal surfaces which are contacted with a petroleum oil at elevated temperatures, and also to provide compositions of matter capable of inhibiting the aforesaid fouling tendency of petroleum oils.